(1) Field of the Invention
The present invention is directed to improvements in cylinder lock systems and, particularly, to cylinder lock systems characterized by having a large number of possible key combinations and by being difficult to defeat. More specifically, this invention is directed to novel keys which cooperate with cylinder locks to define lock systems which provide highly secure access control. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and articles of said character.
(2) Description of the Prior Art
Mechanical locks which employ one or more pin tumbler arrays are well known in the art. In such prior locks, the tumbler pins are arranged in "stacks" which are displaceable, typically in the radial direction with respect to the axis of rotation of a rotatable core or plug, in response to insertion of a key in a keyway provided in the core. The pin tumbler stacks comprise at least an upper or driver pin and an abutting, axially aligned, driven or bottom pin. These pins are disposed in pin chambers provided in both the rotatable core and the surrounding immobilized shell of the lock. The pin tumbler stacks are resiliently biased in the direction of the core and, with the lock in the locked condition without a proper key in the keyway, one pin of each stack bridges the gap between the core and shell thus preventing relative rotation therebetween. As a result of communication between the keyway and the pin chambers in the core which receive the bottom pins of the pin tumbler stacks, insertion of a properly bitted key in the keyway will result in pin tumbler stack displacement which typically places the interface between the driver and bottom pins at a shear line defined by the core outer circumference. Thus, a properly bitted key will permit the core, with the bottom pins, to rotate within the shell while the driver pins remain stationary. Core rotation will, through the action of a cam or tailpiece mechanically coupled thereto, activate a locking mechanism or latch.
Locks of the type generally described above are known in the art as "cylinder" locks. The most common manner of defeating a cylinder lock consists of "manufacture" of an unauthorized key. It is not possible to ensure against the defeat of a cylinder lock by providing such a lock with a keyway having a complex profile, i.e., a very intricate cross-section, and/or through the use of various arrangements of pin tumbler stacks. The foregoing inability is, in part, a function of the fact that various manufacturers will provide, for locks which achieve a significant sales volume, key blanks having blades which, either as manufactured or as shaped using conventional key-cutting machines, have a profile which enables their use, after being "cut", with such locks. Thus, there has been a long standing desire for a lock system which affords increased security through minimizing the possibility of unauthorized manufacture of replacement key blanks and, particularly, for a lock system which affords the lock manufacturer the ability to exercise key control by being the sole source of the key portion of the system.
The requirements summarized in the immediately preceding discussion have been met by the lock systems and associated keys described in U.S. Pat. Nos. 5,819,567 and 5,823,030 both of which are assigned to the assignee of the present invention. The disclosures of the aforemetioned patents are incorporated herein by reference.
In the lock system of U.S. Pat. No. 5,819,567, the core of the cylinder lock includes, at the position of at least one pin tumbler stack, a cut-out which is generally in the shape of a circular segment. With the lock in the locked state, i.e., prior to rotation of the core relative to the shell, this circular segment will be out of alignment with the associated pin tumbler stack. The cut-out communicates with the keyway via an opening provided in a side of the keyway. A plate member or segment is inserted in the cut-out, the plate member being sized and shaped so as to be capable of limited movement within the cut-out and relative to the core. The plate member includes a projection which extends into the keyway and functions as a cam follower. Movement of the plate member relative to the core may be produced by a camming projection, provided on the side of an authorized key, which contacts the cam follower projection when the key blade is inserted in the keyway. The camming projection on the key blade extends outwardly beyond the plane of the side of the blank from which the key was formed. The plate member, when caused to move along a path defined by the shell internal diameter in response to force delivered thereto by the camming projection on the authorized key, will function as an extension of the core and will present a surface which generally corresponds to the shear line defined by the outer diameter of the core. Thus, with an authorized key in the keyway, the core will appear to be uninterrupted to the driver pin of the pin tumbler stack at the location of the cut-out. However, in the case of an unauthorized key which lacks a proper camming projection, core rotation will result in the plate member being displaced below the shear line so as to, in part, define an opening into which the driver pin will move once the core has been rotated relative to the shell sufficiently to fully register the pin tumbler chamber in the shell with the cut-out in the core. The driver pin will, accordingly, move inwardly toward the core so as to bridge the shear line and prevent further core rotation in either the clockwise or counterclockwise direction. The lock will thus be rendered inoperable and the unauthorized key will be trapped in the keyway. When compared to a prior art lock system which lacks the camming projection on the key and the cooperating segment shaped plate with integral cam follower, the lock of U.S. Pat. No. 5,819,567 substantially increases the number of possible combinations since a circular segment cut-out can be located at any one of, or at a plurality of, the locations along the length of the keyway which are defined by the pin tumblers. The number of possible combinations is additionally increased by the ability to change the size and shape of the cooperating cam follower and key blade camming projection.
Both the degree of security afforded by and the number of possible combinations of the lock system of U.S. Pat. No. 5,819,567 can be further increased by the invention of U.S. Pat. No. 5,823,030. The invention of U.S. Pat. No. 5,823,030 includes, as part of the biting, a specially shaped recess in the side of the key blade which is disposed oppositely with respect to the side from which the camming projection extends. With the key inserted in the keyway, this recess is in registration with a chamber in the core which receives an auxiliary locking pin. This chamber, most expediently, is oriented such that its axis is transverse to a plane defined by the side of the blank from which the key was formed. The auxiliary locking pin is resiliently biased outwardly by a spring whereby a first end thereof engages a cooperating recess in the inner diameter of the shell, i.e., the auxiliary locking pin bridges the shear line with the lock in the locked state. The outwardly disposed first end of the auxiliary locking pin and the side wall of the cooperating recess in the shell are cooperatively shaped such that relative rotation between the core and shell will, if movement of the auxiliary locking pin toward the keyway against its spring bias is possible, cam the auxiliary locking pin out of the recess in the shell. Once the auxiliary locking pin is released from engagement with the shell, the outwardly disposed first end thereof slides on the internal diameter of the shell during further core rotation. The release of the auxiliary locking pin from its engagement with the shell, however, can occur only when a key blade having a recess sized, shaped and located to receive the second end of the auxiliary locking pin is present in the facing side of a key blade inserted in the keyway. Thus, in the invention of U.S. Pat. No. 5,823,030, an authorized key must, in addition to the conventional or prior art biting and a correct profile, have both at least a first uniquely shaped and positioned camming projection on a side of the blade and at least a first properly positioned and shaped locking pin receiving recess on a side of the blade.